dayis



6 Sheets-Sheet 2.

(No Model.)

J. P. DAVIS. TELEPHONE BXGHANGB SYSTEM.

No. 331,186. g2/Patented Nov. 24. 1885.

GMO

N. PETERS. Pham-Limusmpm. wnihingwn, D4 c.

(No Model.) 6 Sheets-Sheet 3.

J. P. DAVIS. TELEPHONE EXCHANGE SYSTEM.

No. 331.136. Patented Nov. 24. 1885.

.mlHHlmlllIlr N. PEYERS, Phawllmagmpher. wnshingm, D4 C.

(No Model.) e sheets-sheet 4. J. -P. DAVIS. TELEPHONE EXCHANGE SYSTEM.

N0. 331,186. Patented NOV. 24. 1885.

:Imi I 746591466 Jew jowwyoy,

N. Firms. Pnourumugnpm. wnshsngmn, D. c,

(No Model.) 6 Sheets-Sheet 5.

J. P. DAVIS. TELEPHONE EXCHANGE SYSTEM. 110.331,186. Patented Nov. 24. 1885.

-illll 1 1% N. PETERS. Phnmulmgnpher. washngxon, n. C.

(No Model.) 6 sheets'sheet 6.

' J. P. DAVIS.

TELEPHONE BXGHANGB SYSTEM. No. 331,186. Patented Nov. 24. 1885.

IlNrri-:n @raras PATENT Ottica JOSEPH P. DAVIS, OF NEW YORK, N. Y.

TELEPHONE-EXCHANGE SYSTEM.

SPECIFICATION forming part of Letters Patent No. 331,186, dated November 241. 1885.

Application lcd May 12, 1885. Serial No. 165,197. (No model.)

To all whom t may concern.-

Be it known that I, JOSEPH l?. DAvIs, of the city, county, and State of New York, a citizen of the United States of America, have made a new and useful Improvement in rlelephone-Exchange Systems, ot' which the following is a specification.

' In a telephone-exchange system of the general-class to which my improvement relates be made between subscribers.

one class of attendants, whom I designate as "annunciatm-attendants,have nothing what-` ever to do but to receive the calls of the subscribers and indicate upon paper strips the connections required. A second class of attendants, herein designated as operators, trunk and local operators,7 receive directions from the annunciator attendants of connections to A third class of attendants, known as switchmen,77 are employed, whose sole duty it is to make switchconnections as directed by the operators. An operator, upon receiving a card from the ani nunciator-attendant, immediately calls to the particular switchman having facilities for making the particular switch-board connections required, and thereafter said operator makes other connections which complete the operation of placing two subscribers in communiscribers line.

cation with each other. In other exchanges of this class a horizontal bar, or a pair of such bars extending the entire length of the switchboard, have been employed for each sub- Usually these long horizontal bars have heretofore been placed one above another upon the vertical face of the switchboard, and thus the number of subscribers7 lines that could be connected to the switchboard of an exchange was limited to the comparatively few horizontal strips which could be thus arranged upon the face of said switchboard.

I have found that more than about one hun- A dred horizontal bars, placed one above another, make a switch-board whose upper portion is beyond the reach of the switchmen, and that from this fact, where many subscribers lines enter a single exchange, it becomes necessary to employ two or more independent switch-boards. With the old form of switchboard several switchmen are employed to make connections without reference' to the apportionment of the work. Thus any two of the joining two central exchanges.

`board in the exchange.

subscribers lines may be connected by any one of the several switchmen-that is, they may be connected first by one switchman, then 1 There are local operators whose duty it is to y make connection between any two subscribers whose lines both come into the sameexchange,

and there are trunk-line operators who are l employed to connect two subscribers whose lines enter different exchanges. Trunk-operators join subscribers through a trunk line That part of the switch-board to which one operator is aslsigned is known as a sectional switchboard, and said sectional switch-boardis divided into a series of sub-sections, there ybeing as many sub-sections upon each sectional board as there are table operators in the exchange. Each trunk-operators table Lis provided, say, with twenty lines, which extend, respectively, to the twenty sockets of a sub-section of the switch-board. Each :socket of a sub-section on one sectional board i is electrically connected with the corresponding sockets of the same sub-section on the other sectional board. By this arrangement each trunk-operator has twenty lines from his table connecting with every sectional switch- There'are likewise as many sub-sections of switch-plug sockets on each sectional switch-board as there are local operators, and the socket of one sectional switch-board is electrically connected with a corresponding socket of every other board.

Each local operator is provided with, say, twenty-five pairs of lines, which respectively connect with the twenty-ve pairs of switchplug sockets of a sub-section of the switchboard. The switchmen have no means of communicating with subscribers, and they are not `therefore charged with the duty of conversing with subscribers, but are only charged with the IOO Work of making switch-board connections.y The only persons with whom the switchmen have means of communication are the operators, and from these they can receive oral communications, but the switchmen can transmit none in return.

One feature of Amy invention consists in providing` each switchman with a head-telephone which is placed in a local circuit extending to the table of every operator in the exchange, and said local circuit is provided with a springjack at each operators table. Thus an operator can insert his telephonic transmitter in a switchmans line and orally give the necessary directions `for connecting the various -subscribers lines at the switch-board. Each switchman has anl independent local circuit, including` a spring-jack, at each operators table, and each operator is vprovided with as many such circuits and spring-jacks as there are switchmen. By this arrangement any one of twenty or more operators may call any one of half a dozen or more switchmen, and any switchman may make certain electrical connections in the process ofjoining any two subscribers who connect withv the exchange. A convenient number of subscribers lines-say twohundred and fifty-,pass through each of the series of sectional switch-boards in the same exchange, and thence to an annunciatorboard and to earth'. Normally the lines prassing through one sectional switch-board are not connected with the other sectional switchboards. Each subscriber s line enters its switch-board through an electrical cord and a switch-plug which normally rests upon an electrical contact joining the annunciator and earth, andnpon lifting the switch-plug the connection through the annunciator-board isl broken. In response to calls from the operl ators a switchman removes any one of the main-lineswitch-plugs and places it in a socket in theupper part of the switch-board, and thus establishes an electrical connection between a subscriber and the operatorstable.

To join any two subscribers lines coming to the same sectional switch-board, the plugs l forming parts of said lines are placed in the respective metallic sockets Vof any pair upon the sectional board. Y The movement Vof a switch at the local operators table then completes a connection. between the two subscribers. To join two subscribers whose lines boards in the same exchange, the switchman at one board through which the subscribers line enters places the switchplug of said line j ina metallic socket, as does the switchman of the sectional board to which the second line is connected. I Each socket Aon one sectional board being, connected with a corresponding socket in each Vof the others, connection is then made, between the tw'o subscribers linesfat an operators table, the same as though the, switch-plugs lof the` two lines were placed in a Y pair of sockets upon one board. From the trunk-operators.tables trunk-lines extend to distantexchanges. A trunk -operators table'is thus located upon trunk-lines joining two or more central exchanges, and after an operator has directed the switchmen atV the two exchanges to connect two suscribers lines,

one to eachl end of a trunk-line, he joins the two fragments of the trunk -line at his own table, thus completing a circuit which then includes the two subscribers lines. Y

In the accompanying drawings, Figure l is a perspective View of the interior of my exchange, in which A C, A C, A C2, A C3 are four sections of anannunciator-board having as many annunciator-drops as there are subscribers lines entering the exchange. An attendant is employed at each section of the annunciator-board. S B, SB', S132, S B3 are four sectional switch-boards, and a switchman is assigned to each section, through which, say, two hundred and fty subscribers7 lines pass. T T an T T2 are two trunk-line-operators tables, and L T is a local-operators table. Each of said tables is arranged for four operators, who sit at its four sides, and each operator is provided with an entireand independent set of apparatus. y

Fig. 2A is a diagrammatic View of an ex-v change showing sixteen annunciator-sections,y A C, tables T T for twenty trunk-operators, tables L T for four local operators, and eight switch-boards. The relative numbers of annunciator-attendants, switchmen, and operators may be somewhat varied, though I tlnd the foregoing the most advantageous;

Fig. 3 is a front view of a single section of the switch-board to which one switchman is assigned. Fig. 4 Vis a sectional view of a, switch-board. Fig. 5 is a plan View of a trunk-line table, showing four sets ot' appara-l tions through the switch-boards and annunciv ator to the earth. are connected to Vdifferent sectional switch- As shown vin Figs. 4, 7, and 8, a is a subscribers line joining the fixed end of an electrical cord, b, upon which is hung a pulleyblock supporting a weight, c. Cord b also passes over fixed pulleys d and d', and is joined to the'cylindrical shank p of a switchplug, p3. Said shank is provided with a metalliccollarp*, which normally rests upon a| metallic ring-seat, p', through which the cylindrical shank passes. Each ring-seat p is electrically connected withI an annunciator drop, D?, and the earth by a wire, p9. Each subscribers line at the exchange is provided, with an independent conducting-cord, b, and;

Fig. 6 isan elevation View, partlyjn,

annunciatordrop D2. There are therefore as many cords b and weights c in an exchange as there are subscribers7 lines entering the exchange. The earth connection of any subscribers line through the annunciator-board is broken by the switchman by raising collar p4 from its seat pf, and placing switch-plug p3 in a metallic socket or spring-jacky. In its normal position collar p* is rrnly held upon its seat p by cord b and weight c. To break the annunciator-connection of any line, the weight c is raised and switch-plug p3 is inserted in socket p, and, again, when switchplug p3 is removed from its socket p2,weight c immediately draws shank p back into the ringseat p4 and re-establishcs the earth connection through the annunciator.

As particularly shown in Fig. 3, the section of the switch-board S B is provided with two hundred and ifty switch-plugs, respectively, numbered from 1 to 250, all within the easy reach of a single swtchman, and arranged in ve rows upon the respective shelves P, P', P2, P3, and P4. (See Figs. 1 and 4.) Immediately above the twohundred and fifty switchplugs the central portion of the switch-board is provided with four hundred metallic sockets adapted to receive any one of the two hundred and fifty switchplugs,which are arranged in twenty subsections or groups of twenty sockets each. Said sub-sections or groups are lettered, respectively, from E to X, and each sub-section corresponds with a trunk-operators table, there being as many subsections as there are trunk-operators tables. Each socket p2 in the lettered sub-sections of the switch-board is independently connected by a wire, 5, Fig. 7, to the trunk-operators table,

and. there are therefore twenty wires, 5, leading from atrunk-operators table to the twenty metallic sockets, p2, ofthe corresponding section of the switch-board. The socket-say 10-of section M on switch board S B is electrically connected with socket 10, section M, ofthe other switch-boards, S B', S B, Sto., in the same exchange, and every socket of one sectional board is. in the same manner electrically connected with a corresponding socket of all the others. Thus wire 5, leading from a trunk-operators table, is connected to one socket upon each of the several sectional switch-boards, and said line 5 may be joined i by the switehmen with any one of the sub- 50. There are therefore fifty wires leading to each local-operators table from the respective sockets of the sub-section of the sectional switch-board. Each pair of sockets is,

arranged one above the other, Fig. 8, and to distinguish them from trunk-line sockets I designate them as p12 and p13. Socket p1 is connected by a wire, 12, to the local-operators table, and p13 is connected to the local operators table by a second wire, 13. Socket p1 on one sectional switch-board is electrically connected with a corresponding socket on the p other switch-boards; also socket p13 is connected to corresponding sock ets ofthe other boards. By this means a subscribersline coming into the exchange at switch-board S E may be plugged into connection with wire 12, while a subscribers line coming into the exchange as at switch-board S B4 may be plugged into connection at that board with wire 13, thus enabling any two subscribers7 lines entering the exchange to be joined by the local operator athis table.

In Fig. 8 wire 13 is provided with an annunciator, D, and is connected to S JB, which forms one side of a spring-jack.

S J12 is the opposite side of the spring-jack, to which is connected wire 12.

L S is a switch which normally connects wire 12 with the earth through contact L SC A second fragment of wire, 12, is connected to contact L S2, and when switch L S is thrown to theleft the earth connection is broken and wires 12 and 13 are joined, thereby forming a loop through thelocal-operators table from the switch-board. I

For convenience of illustration, in Fig. 8 I have shown a head-telephone circuit, ht", with only a single spring-jack, S J, at `the local-operators table, extending to theheadtelephone H T oi' the switchman at switchboard S B, though in practice said circuit inc ludes a spring-jack for every trunk and every local operator in an exchange, as is shown in the head-telephone circuit, ht, Fig. 1. 'Each local as well as each trunk operator has an independent spring-jack, S J, and head-telephone circuit for each switch-board in the exchange, whereby .the operator can call any switchman independently of the others. Each local and trunk operator is provided with a telephone-set consisting of a transmitting and receiving instrument embraced in a loop whose ends are respectively connected to the insulated portions q and q of switch-plug Q. Said loop also includes two keys, K and K', which when depressed break the same, but when at back-contact maintain it closed. The switch-plug Q may be inserted in springjack S J, to direct the switchman to make the required connections, and when 'so made the local operator may insert his switchplug Q in spring-jack S J, S Jl, with q in contact with S J12 and q in contact with S J. Vhen Qis thus inserted, the loop-circuit joining the two subscribers7 lines will embrace the telephonie set T T and keys K and K. Upon depressing K the subscribers` line joined to line 12 at the switch-board will be connected to battery M B and the subscriber notified that the desired connec-` IOO IIO

, boards or head-telephone circuits.

tion has been/made. In the same manner K is depressed to notify the subscriber whose line is joined to wire 18 at the switch-board. Each local operator is provided with twentyiive switches, L S, twenty-five spring-jacks, S J1'1 S J11, twenty-five annunciators, D, and as many spring-jacks S J1'1 as there are switch- The annunciator-cases are each provided with a telephone-set, Fig. 8, including a transmitter, T10, and a receiver, T9, a switch-plug, Q5, loopwires 9 9, key K10, and a battery, M B9, one pole of which is connected to earth. Each subscribers line at the annunciator passes through an ordinary spring-jack,thus enabling the annunciator-attendant to insert his switchplug Q5 and converse with any subscriber whose line passes through s his annunciatorboard, or ring the subscribers call-bell, by depressing key K10 and connecting the line with battery M B1.

As has already been stated, while wires in pairs connect the switch-board with the tables of local operators, only single wires connect the switch-boards with the tables of trunkoperators. The wire 5, Fig. 7, which connects corresponding sockets on the various switchboards with a trunk-operators table, is also connected to an anvil, s2, with which switch s is normally in contact, and from which a ci rcuitis completed to earth by wire 6, wire 7, annunciator D, spring-jack S J S J, wire 8, switch s', anvil s1, and wire 8. At the same time trunk link 6 is connected to earth by way of Wire 7, annunciator D, and wires 7 and 8, and thereby annunciator--drop D at the trunkoperators table may be operated either from theswitch-boardin the same exchange or from a distant exchange to which wire 6 is connected. Each switch-board has a battery, L B10, wire c4111, weighted electrical cord b1, weight c1, fixed pulley d10, and switch-plug p10. Now, if the switchrnan desires to operate annunciator D either at a local or atrunk operators table, he places plug p10 in the socket to which the wire connecting with said annunciator is joined, thereby closing a circuit through wire 119, wire 5, and wires 6, 7, and 8 to earth, Fig. 7, or through wires 13 and 12, Fig. 8. Annunciator D is also operated by depressing a key corresponding to K at the distant exchange. 1

The trunk-line operator is provided with'a telephone-set, a switch-plug, Q, keys K K', and battery M B, precisely such as those of the local operators. Each side of a trunkoperators table, T T, (see Figs. 5 and 6,)y has twenty annunciators, D, apair of keys, K K, twenty spring-jacks, S J S J, twentypairs of double switches, S S', twenty sets of switchanvils, s2 s3 s1, and eight spring-jacks, S J 2, S J1, S J 1, S J 5, tc., though only four are *here shown. Y Figs. 7 and 1 show three spring-jacks, S J1, S J1, S J1, three circuits, ht ht ht, and three headtelephones,HT,H 'l1/,H T2, for the switchmen at switch-boardsS B, S B', andS B1. These circuits show only one spring-jack in each,

though in practice, as before stated, and as is indicated in Fig. 1, each of said circuitsfis provided with as many springs-jacks as there are trunk and local operators.

The method of operation in this system lis as follows; Asubscriber desiring to communicate `by telephone with another subscriber whose line is connected to the same exchange, calls by operating his annunciator-drop at the exchange, the annnnciator attendant 'inserts his telephone in the subscribers line and inquires what is wanted. Upon receiving an answer he writes two numbers upon a card,

` one indicating the subscriber who has called and the other the subscriber with whom the Y same switch-board the local operator also directs the same switchman to place the switchplug of the second subscribers line in the upper socket of 201. If, however, the line of the subscriber called passes through one of the other switch-boards instead, the operator must remove switch-plug Q from spring-jack Y SJ14 and place it in the spring-jack ofthe other switchrnans telephone-circuit. The operatorwill then direct the second switch man to place the switch-plug of the line of the subscriber who has been calledfor in the upper socket, 201, of his own switch-board. rlhe line of the calling subscriber has now been 'disconnected `from its normal earth contact and joined with wire 12, while the line of the second subscriber has also been disconnected from its normal earth and is connected to wire 13. The local operator then moves switch L S from anvil L S to L S1, thereby breaking the earth connection of wire 13 and joining it to wire 12. The two subscribers now having been connected the local operator places switch-plug Q in spring-jack SJ12 S-J13 and successively depresses keys K and K. By depressing K the call-bell of the subscrib- .er with whom it is desired to communicate is operated, and by depressing key Ka signal is also transmitted to the calling subscriber. The subscribers are thus notified that their lines have been connected. Switch-plug Q may remain in the spring-jack S J12 S J13 during the conversation between the two subscribers, or it may be removed to be again employed in connecting other subscribers. If the switchman ndsthe line with-which it is desired to connect busy, he places switchplug p1, Fig. 7, in the socket 2011, and -thus actuates annunciator-drop D, which indicates to the local operator that the subscriber called for is engaged. The trunk-line operator re- ICO ceives notice of any desired connection either 4 other exchange.

vline with the trunk-operators table.

If notified by card by the annunciatorattendant in the same exchange that a subscriberwh oseline enters theexchange desires to be connected with a subscriber whose line enters another exchange, the trunk-line voperator first orders the switchman, who sits with a telephone to his ear, to connect the callvingsubscribers line with a certain line, Vas 5,

Fig. 7, which connects the operator7s table with the switch-board,thus joining the subscribers The trunk-operator next inserts switch-plug Q in spring-jack S J S J and rings an alarm or operates a drop at the distant exchange by depressing key K. Further communication between the trunk-operators at the two exchanges is carried on by telephone When the second subscribers line at the distant exchange has been connected to the trunk-line, the trunkoperator moves switch-arm S from S2 to S, and S is moved from S5 to S2, thereby breaking the earth connection through wire 8 and joining wires 5 and 6 into a trunk-line between the two exchanges. Switch-plug Q still remains inserted in spring-jack VS J S J and keys K K are alternately depressed, and the two subscribers are thereby notified that their lines are joined. Should the switchman find a line engaged with which hehas been ordered by a trunk-operator to connect to thetrunk-table, the switchman, instead of plugging the subscribersline into connection with the trunk-table, will place his local switchplug p10 in the same socket, and thereby actuate annunciator-drop D by the agency of battery L B10, the same as in the preceding case respecting the local table. A subscribers line, when plugged into connection with an operators table, is severedv from its normal earth connection at the switch-board, and the circuit of the subscriber is l only completedto earth at the operators table. If all earth connection were broken at the exchange, the subscriber would be unableto transmit a call in case his line were by mistake plugged into connection with the table of an operator. To guard against such error a second switch, S, is employed, Fig. 7, whereby the wires 5 have a normal earth connection through annunciator-drop D. Thus should a switchman plug a subscribers line into connection with an operator not expecting to be joined with such subscriber the operator would first be notified through his drop D of the accidental connection, and could immediately direct the switchman to correct his error. If wire 5 were left op'en at S2,the subscriber would have no means for indicating that his line was opened and his call unanswered. It is obvious that two switches, S and S, as shown in Fig. 7, are not required at a local table, as in Fig. 8. In case of a local table,the calling operator is first joined to the upper wire, 13, and is thereby connected to earth through drop D. By this means the calling subscriber, if connected to the wrong operator by mistake ofthe switchman, may immediately thereafter be joined with the right one. The line of the second subscriber if not at rst connected with the operator as directed by the latter another call from said operator will correct the error.

What I claim, and desire tov secure by Letters Patent, is-

l. In a telephone-exchange, the combination of a series of subscribers7 lines, a series of sectional switch-boards, and an annunciator-board through both of which said lines pass, and an operators table which is in electrical communication with each of the series of sectional switch-boards.

2. In a telephone exchange, the combina- 'tion of an operators table which is in communieation with an annunciator-board from which directions for line-connections are sent, aseries of sectional switch-boards to all `of which directions are sent from each operators table, switching devices for connecting the subscribers lines with the operating-tables at the switch-board, and switching devices at the operating-table for joining the subscribers lines together.

3. In a telephone-exchange, the `combination of a series of subscribers lines passing through each respective sectional switchboard, aseries of sectional switch-boards, and an annunciator-board through which said lines pass to earth, an operators table which is in communication with the annuciatorboard and with each of the sectional switchboards, switching devices for disconnecting the normal earth connections of the subscribers7 lines and joining them to the operators table, and switches for connecting the subscribers lines together at the operators table.

4. In a telephone-exchange, the combina` tion, with a series of sectional switch-boards through which independent groups of subscribers7 lines pass, annunciator calling devices independent of the switch-boards, an operators table with which the subscribers lines are connected by the switchmen at the direction of the operator, and switching devices for joining the lines together at the operators table. l

5. In a telephoneexchange, the combination of a series of sectional switch-boards through which the subscribers lines pass, an operators table to which the subscribers lines are connected by the switchmen, and a telephonecircuit from the operators table to each switchman.

6. In a telephone-exchange, the combination of a switch-board through which subscribers lines pass, a series of wires joining the switch-board with an operators table, a head-telephone for the switchman in a local circuit extending to the operators table, and an operators telephone in said circuit at'the operator s table.

7. In a telephone-exchange, the combination of a series of sectional switch-boards IIO through each of which subscribers7 lines pass Y to earth, one or more pairs of wires joining each sectional switch-board and alocal operators table, one wire of each pair being normally open at the operators table and the other connected to earth through an annuntogether, a spring-jack in said loop, and a telephone-set, and aswitch-plug for connecting the sanne in said loop.

9.'In a telephone-exchange, the combination of a switch-board through which subscribers lines pass to earth, a loop extending from the switch-board to an operators table, a local circuit for the switchmans telephone, a spring-jack in the loop, and a spring-jack in the switchmans telephone-circuit at the operators table, a telephone-set, and a switchplug for joining said telephone either in the loop or in the switchmans telephone-circuit.

10. In a telephone-exchange, the combination of a series of sectional switch-boards through each of which subscribers lines pass to earth, a trunk-operators table, one or more wires joining each sectional switch-board with said operators table through an annunciatordrop and to earth, one or more trunk-lines extending from the earth at the trunk-operators table `toadistantexchange,and a switch, both for disconnecting a wire from the switchboard and the trunk-line from earth at the operators table and connecting them together.

11. In a telephone-exchange, the combination of a series of sectional switch-boards through each of which subscribers lines pass to earth, one or more wires joiningtheswitchboard with the trunk-operators table, one or more trunk-lines joining said operators table and a distant exchange, and a switch for joining one of the-wires from the switch-board with a trunk-line at the operators table.

12. In a telephone-exchange, the combination of a switch-board through which subscribers lines pass to earth, a trunk-operators table, a trunk-line` and a spring-jack therein at the operators table, a local telej phone-circuit between the operatorstable and the switchman, a spring-jack therein at the operators table, a telephone-set, a switchplug and signaling-keys KK', and battery M B, as and for the purpose described.

13. In atelephone-exchange, the combination of a series of sectional switch-boards through each of which subscribers lines pass, an operators table, a wire joining said operators table and corresponding sockets upon the several switch-boards.

14. In a telephone-exchange, the combination of a series of sectional switch boards through each of which subscribers lines pass to earth, two wires, each of which connects corresponding sockets upon the several switchboards and is then connected to a local-operators table.

15. In a telephone exchange, a switchboardthrough which subscribers lines pass, a series of conducting-cords and plugs which normally connect said lines to earth, a series of switch-plug sockets upon said board which are separately connected to operators tables, the whole being so arranged that the cordswitch plugs may be removed from their normal positions and placed in said sockets, thus breaking the normal earth connections of the subscribers lines and connecting the same with the operators tables.

16. A sectional switch-board which is provided, rst, with as many cord switch-plugs as there are subscribers lines passing therethrough,and, second, with several sub-sections or groups of switch-plug sockets, the sockets of each sub-section being all independently connected with an operators-table.

17. A sectional switch-board for a telephone-exchange, which is provided, first, with a series of cord switch-plugs; second, with several sub-sections or groups of switch-plug sockets,each sub-section being connected to aseparate trunk-operators table, and, third, with several sub-sections of switch-plug sockets, each sub-section in pairs being connected with a local operators table, substantially as described.

18. In a telephone-exchange, the combination of several sectional switch-boards for a series of switchrnen, a series of operators tables, and a head-telephone for each switchman,placed in a local circuit leading to every operators table in the exchange.

19. In a telephone-exchange, the combination of a series of sectional switch-boards each having corresponding sub-sections of switchplug sockets, in which corresponding sockets of the same sub-section of the several sectional boards are connected together, and in which the several sockets of a sub-section are connected by independent wires with an operators table, whereby each operator has several wires with which any swi'tchman in the exchange may make connection.

2 0. In a telephone-exchange, the combination of a switch-plug and battery at the switchboard, a series of switch-plug sockets upon said board, to which wires are joined withoperating-tables, and an annunciator for each ksuch wire at the operators table.

JOSEPH P. DAVIS.

Witnesses:

J. A. SEELY, H. 1?. OornLAND.

IOO

IIO 

